Well,thank you *Zhora I will feel free to add to this 
I personally think the law is actually quite clear on this (if fundmentally and abhorrently flawed by stealing women's morally inalienable rights in the first place, amongst other flaws).
Single sex exemptions can apply. Needs of competing groups must be balanced (again even if the premise is flawed) and if exemptions are to be made, the least discriminatory option should be chosen.
The problem we have I think is in getting men/organistions to give any importance to women's needs when they do the balancing; women rarly score any points. This is the misogyny.
Reading one of the prison judgements re the male who was moved to a women's prison, the other day I was struck by just little weight the judge gave to the consideration of the risk/ suffering to women, and how dismissive his attitude. He briefly and superficially acknowledged a risk, but as if it were merely theoretical rather then being the suffering of actual human beings, woman) and so scored it as of little to no importance.
ALL the importance was given to the needs/ suffering of the male. Women scored 1 out of 10 for severity of needs, the male scored 8 out of 10 = male wins on balancing. The biased misogynist judgement makes bad law even worse and this is not justice or equality.
Women's toilets (and other spaces) were always for females Zhora only morally bankrupt people would argue otherwise. TRA attempts to re-define words to include transwomen as women to try to justify the unjustifiable theft of women's rights is not as clever as you think it is. The desperate acts of unstable and irrational men.
As Barracker said on the Debbie Hayton thread, even having a GRC gives "a legal mandate (from men over women) It is not a moral one. It has always been immoral.